The proposed experiments are designed to examine the physiology of circadian and photoperiodic systems in lizards. The roles of the pineal organ and its hormone, melatonin, the suprachiasmatic nucleus of the hypothalamus, and the eyes will be examined as components of the lizard's circadian system. Lesions of the suprachiasmatic nucleus, pharmacologic manipulation, HPLC fractionation, and melatonin infusions will be employed to explore the role of these areas and to assess how these areas are coupled to each other and to the photic environment. All animals, including man, show daily cycles in many aspects of their biology and behavior. Daily rhythms in sleep-wakefulness, hormone levels, brain activity, and body temperature are only a few of the literally hundreds of cycles that have been described. These rhythms are all caused by an internal time-keeping system commonly termed the "biological clock". Disruptions of biological clocks have detrimental effects on the animals' well being. These studies utilize a lower vertebrate, the reptile, as a model to analyze the locations of components of the biological clock and to discover how these clocks are influenced by signals from the environment - such as light and temperature. These studies will give us insight into how the time-keeping system of vertebrates is organized and should allow us to manipulate the system appropriately.
